How can I improve server-side code to avoid causing 500 errors when handling AJAX requests?

Focus on writing robust and error-free server-side code. Validate all user input to prevent injection vulnerabilities and unexpected data. Use try-catch blocks to handle potential exceptions gracefully. Implement proper database connection management to avoid connection timeouts. Write unit tests to verify the correctness of your code. Ensure your code adheres to coding best practices and security guidelines.